Infomercials are long-format television commercials, typically five minutes or longer. Infomercials are also known as paid programming (or teleshopping in Europe). This phenomenon started in the United States where infomercials were typically shown overnight (usually 2:00 a.m. to 6:00 a.m.)--outside of peak hours. Some television stations chose to air infomercials as an alternative to the former practice of sign-off. By 2009, most US infomercial spending is during early morning, daytime, and evening hours. Stations in most countries around the world have instituted similar media structures.

The term "infomercial" is sometimes misapplied and used to refer to direct response television advertisements (DRTV) of 60 to 120 seconds in length. However, the term describes program length advertisements which, in the US, are typically 28 minutes and 30 seconds in length (see above references). In the US, DRTV advertisements of 30 seconds to 2 minutes in length are typically called "short form" or "DRTV spots" and are not included in the advertising industry's use of the term "infomercial". Note that in the US market, a small amount of media can be purchased for 5 minute length advertisements, although this time is quite limited. Outside of the US market, lengths depend on the lengths allowed by television stations and government regulators.

While the term "infomercial" was originally applied only to television advertising, it is now sometimes used to refer to any presentation (often on video) which presents a significant amount of information in an actual, or perceived, attempt to persuade to a point of view. When used this way, the term may be meant to carry an implication that the party making the communication is exaggerating truths or hiding important facts. Often, it is unclear whether the actual presentation fits this definition because the term is used in an attempt to dis-credit the presentation. In this way, political speeches may be derogatorily referred to as "infomercials" for a specific point of view.